FIGS. 9 and 10 represent an example of conventional flowmeters for measuring the flow rates of flowing liquids (ref. U.S. Pat. No. 3,953,819). This flowmeter 100 is composed mainly of a flange 101, housing 102, vane 103, revolving pin 105, potentiometer 106 and torsion spring 107. Said vane 103 is fixed at one edge to the revolving pin 105 in such a manner as to be able to rotate in opposition to the force of said torsion spring 107 and said revolving pin 105 is fixed to a slider in the potentiometer 106, so that electrical signals corresponding to the rotation angles of the vane 103 can be transmitted through lead wires 108. Said flowmeter 100, as shown in FIG. 10, is placed in a passageway 109 for liquids and fastened to the conduit 110 with the flange 101 bolted on and at such a position that the revolving pin 105 of the vane 103 makes right angles with the axis of said passageway 109 and that in the passageway 109 the free edge of the vane 103 meets the edge of a partition 111 which is raised from under at right angles with the axis of the passageway 109, the center of said free edge of the vane 103 coinciding with the axis of the passageway 109.
The fluid which flows through said passageway 109 causes said vane 103 to turn at an angle corresponding to the velocity of the flow. Such a flowmeter 100, therefore, is capable of measuring the volumetric flow of the fluid as a function of the angle at which the vane 103 turns.
Such a flowmeter of the conventional type measures the resistance which affects the flow as it passes the vane 103 in terms of the difference in pressures of the flowing fluid between the two sides of the vane 103 (i.e. the angle at which the vane 103 turns). Thus a conventional flowmeter is capable of measuring the flow rate in terms of volumetric value, but not the mass flow rate. Herein lies a problem in that a conventional flowmeter is unable to determine the exact flow rate where, for example, cavitation occurs or bubbles are formed in the flow. A further problem arises in that a conventional flowmeter cannot determine the current flow rate under conditions where the temperature is not stabilized, because the changes in viscosity of a fluid caused by changes in temperature influence the resistance which affects the flow.
Accordingly, it is an object of the present invention to provide a flowmeter which is designed to determine the mass flow rate by measuring changes in momentum of a flowing fluid so that measurement of a flowing fluid will not be influenced by changes in temperature and accurate measurement will be possible where cavitation, bubbling, or the like occurs in the flow.
It is another object of the present invention to provide a flow control valve which is designed to regulate the flow of a fluid by detecting changes in momentum of the flow, which are proportional to the mass flow rates, so as to be capable of adjusting a flow to a prescribed rate in terms of mass flow accurately without being influenced by changes in viscosity of the fluid or where cavitation, bubbling, or the like occurs in the flow.
It is another object of the present invention furthermore to provide a hydraulic apparatus which is designed to variably control the discharge from a variable displacement pump by detecting changes in momentum of the flowing fluid, which are proportional to the mass flow rates, so that the rate of discharge from said type of pump will be accurately controlled to a prescribed rate without being influenced by changes in viscosity of the fluid or where cavitation, bubbling, or the like occurs in the flow.